Multi-stage axial compressor

ABSTRACT

The compressor is formed with a sealed casing chamber in which the stator blade adjusting mechanism is mounted in sealed relation to the main gas flow path. This chamber is pressure equalized with the inlet duct of the compressor by means of a connecting duct so that any leakage into the casing chamber can be quickly eliminated.

United States Patent [191 Benz [ 1 Sept. 30, 1975 MULTl-STAGE AXIAL COMPRESSOR [75] Inventor:

[73] Assignee: Brown Boveri-Sulzer Turbomachinery, Ltd., Zurich, Switzerland [22] Filed: Aug. 23, 1973 [21] Appl. No.: 390,898

Hans Benz, Winterthur, Switzerland [58] Field of Search 415/148, 149, 108, 199 A, 415/53, 106, 104, 168

United Kingdom 415/108 United Kingdom 415/53 Primary E\'alm'ner--Henry F. Raduazo Attorney, Agent, or Firm-Kenyon & Kenyon Reilly Carr & Chapin [5 7 1 ABSTRACT The compressor is formed with a sealed casing chamber in which the stator blade adjusting mechanism is mounted in sealed relation to the main gas flow path. This chamber is pressure equalized with the inlet duct of the compressor by means of a connecting duct so that any leakage into the casing chamber can be quickly eliminated.

[56] References Cited FOREIGN PATENTS OR APPLICATIONS 2 Chims 4 Drawing Figures 531,926 10/1954 Belgium 415/149 .1 in, I I, I l il| I am a g -Um nu ml 9-- l, 1| l .5 13 =1 A 72 1 \*':*F-''''-'- a U.S. Patam Sept.30,1975 I 3,909,153

MULTI-STAGE AXIAL COMPRESSOR This invention relates to a multi-stage axial compressor having adjustable stator blades.

Heretofore, compressors have generally been constructed with an inlet duct, compressing chamber and outlet duct. Usually, the compressing chamber has had rotor blades and adjustable stator blades mounted therein for purposes of compressing a gas passed through the chamber. However, where gases containing moisture are pumped, there is a risk of gas ingressing, particularly from the high-pressure side, into the locations in which the stator blade support and the associated adjusting mechanism have been disposed. Should the gas cool on the usually colder casing walls on the inlet side, liquid can be precipitated. This may result in corrosion, particularly on the stator blade bearings and on the adjusting lever slide-blocks and in the associated slots usually provided in the compressor.

Accordingly, it is an object of the invention to eliminate the causes of corrosion, as far as possible, on the blade adjusting mechanism of a compressor.

It is another object of the invention to seal the stator blade adjusting mechanism of a compressor from the effects of a gas being compressed. I

It is another object of the invention to eliminate as quickly as possible any moisture that may occur in the environment of a stator blade adjusting mechanism.

Briefly, the invention provides a multi-stage axial compressor having a casing, an inlet duct and an outlet duct with a stator blade support which serves to define a sealed casing chamber between the casing and support and between the inlet and outlet ducts. In addition, stator blades are sealingly mounted in the support and an adjusting mechanism is mounted within the casing chamber. Also, a connecting duct communicates the inlet duct with the casing chamber to equalize the pressure therebetween. The individual stator blades are sealed at the position at which they extend through the stator blade support. In this way, the amount of leakage which ingresses into the casing chamber is minimized and the connecting duct ensures that the casing chamber is under the suction pressure to which the ingressed leakage quantity is expanded without risk of liquid precipitation before being discharged to the suction side, i.e. the inlet duct. To this end, the cross-section of the connecting duct should be kept as large as possible in order to permit rapid discharge of the leakage without giving rise to a substantial pressure gradient with respect to the suction chamber.

As is known, the appearance of dewpoint effects in the casing chamber can occur if the pressure in the chamber rises above the suction pressure and if there is an increase in the time during which the gas which contains the moisture dwells in the chamber or on the cold external walls of the chamber. Thus, in order to permit a rapid discharge of condensed liquid from the casing chamber which may occur despite the above measures, the casing of the compressor is provided with a trough-shaped indentation whose lowest position is connected to the connecting duct. Since any leakage flows would occur more particularly from the highpressure side, the connecting duct is also positioned to merge into the casing chamber near the high-pressure side. This will reduce the period of time during which the moisture laden gases remain in the casing chamber.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 diagrammatically illustrates a vertical sectional view through an axial compressor according to the invention;

FIG. 2 illustrates a detail A of FIG. 1 relating to the transition between the compressor casing and the stator blade support through which the casing chamber is separated from the suction side of the flow duct;

FIG. 3 illustrates a detail B of FIG. 1 relating to the transition between the compressor casing and stator blade support through which the casing chamber is separated from the high-pressure side of the flow duct; and

FIG. 4 diagrammatically illustrates a seal between the flow duct and the casing chamber for one stator blade.

Referring to FIG. 1, the multi-stage axial compressor has a casing l in which a rotor 2 is rotatably mounted. As shown, the rotor 2 is mounted at the ends in separate bearing blocks 3. The casing 1 includes a suction duct 4 at one end, a casing chamber 5 and a high pressure outlet duct 6 at the other end. The casing chamber 5 is disposed in the middle of the compressor and accommodates an adjusting mechanism 7 for a plurality of stator blades 8. As shown, the casing chamber 5 is defined by a stator blade support 9, by an external wall 11 of the casing l and to both sides by a Wall 12 of the suction duct 4 and by a wall 13 of the outlet duct 6. The stator blades 8 project through the support 9 into a flow duct 10 within the support 9.

Since no sealing is required with respect to the suction side, the stator blade support 9 is merely inserted by means of an annular projection 14 into a corresponding annular groove 15 of the suction duct wall 12 as shown in FIG. 2. On the delivery side, the stator blade support 9 bears via a collar on a shoulder of the outlet duct wall 13, as shown in FIGS. 1 and 3, and is axially slidable thereat to allow for thermal expansion. The casing chamber 5 is sealed with respect to the highpressure duct 6 by means of a seal 16 (FIG. 3) which may be constructed of rubber or of metal depending on the prevailing temperatures.

Referring to FIG. 4, the root of each stator blade 8 is also provided with an annular groove in order to minimize the leakage which might occur at the position 17 of the blade support 9 through which the blade extends. A sea] element 18, in the illustrated example, an O- ring, is also inserted into the annular groove.

An inlet duct 19 of the compressor which merges into the suction chamber 4 also communicates at a point upstream of the stator blade 8 through a connecting duct 20 with the casing chamber 5. The connecting duct 20 extends from a position in the inlet duct 19 to a position 21 in the casing chamber 5. The position 21 at which the duct 20 is connected to the casing chamber 5 is advantageously disposed at the lowest position of the chamber 5. Further, the casing wall 11 is provided with a trough-shaped indentation 22 near the position .21 in order to facilitate flow of any.liquid into the connecting duct 20. The position 21 is also disposed as far as possible near the end of the chamber 5 which is nearest to the high-pressure outlet duct 6 because the largest amounts of leakage are to be expected from the delivery side and may thus be discharged as rapidly and as directly as possible. What is claimed is:

1. A multi-stageaxial compressor comprising a casing;

an inlet duct in said casing for the ingress of a gas to be compressed;

an outlet duct in said casing for the egress of compressed gas;

a stator blade support located between said ducts within said casing to define a sealed casing chamber between said casing and said stator blade support and between said ducts;

a plurality of stator blades sealingly mounted in said 1 stator blade support;

an adjusting mechanism within said casing chamber for adjusting said stator blades; and

a connecting duct outside said casing chamber communicating said inlet duct with said casing chamber to equalize the pressures therebetween, said duct merging into said casing adjacent said outlet duct; 

1. A multi-stage axial compressor comprising a casing; an inlet duct in said casing for the ingress of a gas to be compressed; an outlet duct in said casing for the egress of compressed gas; a stator blade support located between sAid ducts within said casing to define a sealed casing chamber between said casing and said stator blade support and between said ducts; a plurality of stator blades sealingly mounted in said stator blade support; an adjusting mechanism within said casing chamber for adjusting said stator blades; and a connecting duct outside said casing chamber communicating said inlet duct with said casing chamber to equalize the pressures therebetween, said duct merging into said casing adjacent said outlet duct at a low position in said casing chamber and extending to said inlet duct at a point upstream of said stator blades for draining condensed liquid from said casing chamber into said inlet duct.
 2. A multi-stage compressor as set forth in claim 1 which further comprises a trough-shaped indentation in said casing within said casing chamber at said low positions, said indentation having a lowest position in communication with said connecting duct. 